The present invention generally relates to an engine inlet system for a turbofan propulsion engine and, more particularly, to an engine inlet system that is capable of separately diverting boundary layer air and free-stream air into a turbofan propulsion engine
In conventional aircraft design, the wings of the aircraft provide aerodynamic lift and further support the weight of the fuselage. Engines are then coupled to the wings and/or the fuselage to provide thrust for propelling the aircraft.
However, recently there have been significant developments into the design of xe2x80x9cblended wing-bodyxe2x80x9d aircraft. In a blended wing-body aircraft, the fuselage and wings are joined to form a smooth curve along the exterior of the aircraft with no discrete interface between the fuselage and the wing. In order to maintain the aerodynamic efficiency and lift characteristics of a blended wing-body aircraft, it has been determined that an aft-mounted engine configuration provides the least disturbance of airflow over the wing-body surface, thereby maintaining the aerodynamic efficiencies and advantages of the blended wing-body design.
Aerodynamic lift is the result of the movement of fluid (e.g. air) over the surface of the wing. According to the laws of fluid dynamics, such fluid movement produces a boundary layer between a region of low static pressure and a region of high static pressure. According to current wing design technology, it is preferable to keep this boundary layer attached along a wing surface in order to delay or totally prevent flow separation. Such delay or prevention of the flow separation improves the aerodynamic characteristics of the wing surface, thereby providing a wing that produces less drag relative to a wing having a separated flow field.
During flight, the boundary layer air that typically forms along the wing surfaces and fuselage is of low velocity and low static pressure. Because low energy air causes poor engine performance, some aircraft have employed some type of boundary layer diverter system to prevent the boundary layer air from entering the engine inlet.
Present boundary layer diverters require various subsystems or add on baffles to make them work properly. Such subsystems and/or baffles may increase the weight, the cost of production, mechanical complexity, and the cost of maintenance of the aircraft. Also, the engines would be mounted higher up, causing nose-down moments and increased wetted area.
On the other hand, in the case of a blended wing-body aircraft, when the engines are mounted generally flush with a trailing edge of the effective wing, the mixture of boundary layer air and free stream air causes distortion in a combined inlet. That is, simply aft mounting engines to a blended wing-body aircraft may produce poor aerodynamic efficiency of the effective wing surface and may cause poor engine efficiency due to the intake of low energy boundary layer air.
Accordingly, there exists a need in the relevant art to provide an engine inlet system for a turbofan propulsion engine that is capable of separately diverting boundary layer air and free-stream air to a turbojet propulsion engine. Furthermore, there exists a need in the relevant art to provide an engine inlet system that is capable of maximizing the aerodynamic efficiency of the wing surface and, simultaneously, maximizing the engine efficiency of the jet propulsion engine. Still further, there exists a need in the relevant art to provide an engine inlet system that overcomes the disadvantages of the prior art.
A dual boundary layer engine inlet for a turbofan propulsion engine of an aircraft having an advantageous construction is provided. The engine inlet includes a first air inlet positioned generally within the boundary layer flowing around the exterior surface of the aircraft. A first passageway fluidly interconnects the first air inlet and the jet propulsion engine to provide air from the boundary layer to the bypass to reduce aerodynamic drag. A second air inlet is positioned generally outside of the boundary layer. This second passageway fluidly interconnecting the second air inlet and the turbofan propulsion engine to provide free-stream air outside of the boundary layer to the core and compressor of the turbofan engine to maintain engine efficiency.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limited the scope of the invention.